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#4812616 - 07/12/18 07:57 PM 5w20 vs 5w30?
klt1986 Offline


Registered: 04/08/09
Posts: 393
Loc: Southern VA
Would a 5w20 and 5w30, such as Mobil 1, Pennzoil Platinum, Valvoline Synthetic or Castrol Edge, have the same cold startup viscosity? I understand once the oil is at operating temperature, one should act as a 30 weight and the other as a 2o weight. However, wouldn't they both flow the same at startup??
_________________________
Wife: 08 Honda CR-V 4WD, M1 5W-20
Me: 11 Toyota Tundra DC 4WD 5.7L, PP 5W-30
Me Work: 06 Ford Explorer 4WD 4.0L, Pennzoil 5W-30
Son: 14 Toyota Corolla S, M1 AFE 0W-20

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#4812633 - 07/12/18 08:16 PM Re: 5w20 vs 5w30? [Re: klt1986]
CR94 Offline


Registered: 03/20/16
Posts: 1173
Loc: Western S.C. since 1996
About.

Doesn't 5W-30 effectively consist of 5W-20 with a dash of extra VI improver thrown in?
_________________________
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#4812662 - 07/12/18 08:34 PM Re: 5w20 vs 5w30? [Re: klt1986]
Astro_Guy Offline


Registered: 07/30/15
Posts: 453
Loc: Pennsylvania
They would if you were in Fairbanks Alaska in January. The 5w30 should be a little thicker in Virginia.

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#4812679 - 07/12/18 08:42 PM Re: 5w20 vs 5w30? [Re: klt1986]
d00df00d Online   content


Registered: 10/20/05
Posts: 11254
Loc: PA
Originally Posted By: klt1986
Would a 5w20 and 5w30, such as Mobil 1, Pennzoil Platinum, Valvoline Synthetic or Castrol Edge, have the same cold startup viscosity? I understand once the oil is at operating temperature, one should act as a 30 weight and the other as a 2o weight. However, wouldn't they both flow the same at startup??

In sub-freezing temps, they'll be comparably pumpable.

On startup at more moderate temps, most 5W-20s will be thinner than most 5W-30s.
_________________________
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#4812720 - 07/12/18 09:09 PM Re: 5w20 vs 5w30? [Re: klt1986]
bbhero Offline


Registered: 03/20/15
Posts: 4724
Loc: Virginia
Yep. The same. The last couple of winter's with low temps down to as low as -7F in the area... No difference amongst those oils at start up. If it pumps.... It pumps. Which those oil would. If those oils fall back into the sump... It falls back into it. Which those iils would have easily at -5 to -7F. The CCS and MRV with all these oils make them all great for the coldest temps seen in this area. I would not be concerned at all smile


Edited by bbhero (07/12/18 09:10 PM)
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#4812749 - 07/12/18 09:46 PM Re: 5w20 vs 5w30? [Re: klt1986]
bubbatime Offline


Registered: 03/18/08
Posts: 5720
Loc: South Florida
Not the same, but close. Every oil will have its own viscosity, at each temp, measured in centistokes.

So when you say startup, what temp are you talking about? Because in Alaska, the cold start winter viscosity is going to be drastically different than the cold start viscosity in Phoenix in the summer.

One paper I read showed when oil is freezing solid, right below its pour point, it has about 100,000 centistokes. This is about -45 degrees C. At operating temp, 100 degrees C, a synthetic 5W20 has about 9 centistokes.

So a synthetic 5W20 has between 9 centistokes at operating temp, and 100,000 centistokes when the oil is frozen solid and almost pours.

The 5W30 vs 5W20 labeling is a layman's labeling system, to dumb down what the oil does for the average consumer. Most folks wouldn't understand what viscosity oil to buy if it was labeled by centistokes.
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